The disclosure generally relates to a power converter circuit of an illumination system and, more particularly, to the power converter circuit with better compatibility.
In view of the awareness of the energy crisis and the promotion of the environmental protection, many traditional products with poor energy efficiency are gradually replaced by energy-saving products. For example, in the illumination system, low power illumination devices (e.g., light-emitting diodes) are usually utilized to replace traditional illumination devices (e.g., incandescent lamps and halogen lamps) to conserve energy.
Many low power illumination devices are manufactured in the form of standard bulbs or tubes to directly replace traditional bulbs or tubes. For example, light-emitting diodes may be made into T8 tubes, E27 bulbs, and MR16 lamps. It is, however, difficult to replace many circuit elements of the current illumination system already installed in the building (e.g., dimmers, electric transformers, and ballasts). If the traditional bulbs or tubes are directly replaced by the low power illumination devices, the low power illumination devices usually have problem cooperating with the circuit elements installed in the building. Therefore, the low power illumination device may flicker or may not be lighted up.
The electric transformers are so compact that they are usually utilized in the illumination system. The electric transformer comprises oscillating circuits and other circuit elements for providing the required voltage signal with a higher oscillating frequency. The load of the electric transformer must draw enough current to enable the normal operation of the electric transformer. The energy consumption of the low power illumination device, however, is usually far less than the energy consumption of the traditional illumination devices so that the low power illumination device may not draw enough current from the electric transformer. Consequently, the low power illumination device usually ma not function normally when cooperating with traditional circuit elements in the current illumination system.
U.S. Patent Application No. 2012/0169246A1 discloses an illumination device and a driving method to solve the aforementioned compatibility problem by alternately operating the circuit between a current generating mode and an off mode. Even if the technique in the aforementioned application is adopted, the compatibility problem still occurs when the low power illumination device cooperate with the electric transformer. The low power illumination device still may flicker or may not be lighted up.